


Heatisiac

by Sin_Cognito



Category: Undertale (Video Game)
Genre: Fell Papyrus (mentioned), Kinktober, M/M, Mildly Dubious Consent, Papyrus (mentioned) - Freeform, Red - Freeform, Sans (underfell) - Freeform, aphrodisiac, very mildly though
Language: English
Status: Completed
Published: 2017-10-16
Updated: 2017-10-16
Packaged: 2019-01-18 08:23:20
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,596
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12384480
Author URL: https://archiveofourown.org/users/Sin_Cognito/pseuds/Sin_Cognito
Summary: Sans has been waiting for a chance to declare his love for his double from Underfell. Will he get to say it tonight ? Or will the unexplicable heat in his body prevent him from speaking up ?





	Heatisiac

**Author's Note:**

> kinktober prompt : Can I please get a fic with Kustard and aphrodisiacs? Thank you <3
> 
> It started as just pure smut, but evolved into this. Not really dub-con (Sans is completely happy with the situation) but just to be safe…  
> I like kustard but it’s such a popular ship that I always fear I won’t do it justice… So I hope you’ll enjoy my first time messing with them. (also I really need someone to help me with Red’s speech. I REALLY try to make him speak with slurred words and all, but I’m really bad at it… So please be indulgent)  
> Today’s new word is supine : did I use it correctly ?? (if not then please correct me ♥)
> 
> You can send me a kinktober prompt on my tumblr : https://sin-cognito.tumblr.com/

Sans hurried to the door. He may have been the laziest skeleton in the entire multiverse, he couldn't help feeling excited at the idea of spending the evening with Red. Just the two of them...

Papyrus had left earlier to "KIDNAP FELL FOR IMPROMPTU INTENSE TRAINING WITH UNDYNE BECAUSE ONE SHOULD ALWAYS BE PREPARED NYEHEHE !!!" Sans thought it was strange for his brother to have other plans on their weekly MTTV day, but he wasn't about to complain when Red offered he could come anyway and keep him company.

Sans was in love with Red. He never thought he would one day fall in love, even less with another version of himself. But the little crush he had had when the fell universe and his own had merged together had eventually evolved into something deeper. And now Sans was way past the point of feeling insecure or guilty about that. All he could think of was Red. When the gruffier skeleton was around, Sans would lose track of time and simply enjoy bathing in the other's presence. Just being in the same room as Red made him feel... alive.

He had been in this sappy state for about 6 months now. Even Papyrus had caught up with what was happening and was showing support. Though he had assured Sans that him kidnapping Fell tonight had nothing to do with helping the little skeleton's possible love confession, he knew his brother by heart. And thus he was ever so grateful to his brother, the legendary Great Papyrus, to give him this oportunity. There was no way he would let it pass.

 

"guess who brought the booze ??!!"

Red was happily juggling two bottles of deer beer, the fell version of their spider cider. Sans wasn't a huge fan of the beverage, it was a bit too strong for him. But hey, tonight was special right ? Red proceeded to enter, nudging the other skeleton in passing, and fell flat on the couch, the beers jingling together. He must've had noticed Sans' skeptical gaze, because he declared with a strange playful gleam in his eyes : "doncha worry buddy, this one's sweeter than you think".

After Sans brought their usual treats when Papyrus wasn't around, which consisted of more or less cooked fries with infinite rations of mustard and ketchup, they switched on the TV and put it on mute. Their favorite game was replacing Mettaton's grandiose dialogue with their own puns, each shittier than the next. Red was particularly gifted in this domain, and his dark humour would always hit the skull's eye with Sans. Red always knew how to rub Sans' funny bone. If only he would rub his other bones too...

Woh wait. What ?

They continued to share bad puns and good laughs, comfortably buried in the sofa's cussions, the plate of fries on Sans' lap. He could feel Red lying on his shoulder more and more everytime he would grab a fry. He would relish in the most wonderful feeling whenever their hands would accidently touch above the plate. Sometimes, he'd pick a mustardy fry and imagine if that was what Red tasted like. The spicy and pungent flavor would burn his taste buds, but then the unexpected sweetness would appease his wounds... He needed more of that, and his newly formed blue tongue seemed to agree. His mouth began to drool at the prospect of tasting the true origin of this gourmet bliss.

He could already picture himself kissing Red, rubbing his blue tongue against the insanely hot appendage...

WOW WAIT. That wasn't normal... What was...

"you alright sweetie ?"

The most heated of chills traversed his entire body and settled in his aroused soul. Red's rumbling voice was such a turn on. He briefly wondered why he was aroused in the first place, but his mind was sooo fuzzyyy... All he knew and could focus on was Red's beating soul, radiating with warmth, and so inviting...

But his eyes were lured by Red's own crimson eyelights. He vaguely processed the other grabbing his bottle of beer before coming closer, his breath only one sigh away. Oh, if only in Red's hand wasn't a beer, but Sans's own d...

Sans caught sight of Red's ecto-tongue when he began drinking from the bottle, though it would be more accurate to say he was sucking the bottle, some of the liquid escaping and running down his chin. He had the entire neck of the bottle shoved deep in his throat and he was making deliciously intoxicating sounds... Sans was captivated by the back and forth movements of Red's skull on his di... on the bottle. The beer bottle.

Then Red's hand was on his cheek.

And his lips on his own.

He felt the pungent nectar slide on his tongue, and finally, at last, got to taste the object of his desire. Red's sinful appendage intertwined with him in a slow but burning ballet. In their eagerness to dance together, they forgot about the outside world, their universe reduced to the heated waltz of their touching magic. Neither seemed to want to let the other go. They were fine making out on the couch for all eternity. In a weak attempt to ground himself to reality, Sans grabbed Red's hood and pulled him closer. The two bodies seemed to communicate more than their heads, and soon Sans was pinned under Red's formidable stature.

To both their surprise Red broke the kiss, and despite Sans' heavy protest, he moved away from the supine skeleton. He tried bringing him closer again but he couldn't do anything against Red's powerful grip on his wrists. Unable to voice his discontentment in the turn of events, he just pitifully moaned.

"hush now dollface and listen to me. i havent been totally honest with ya." Red's voice was breathier than usual. If Sans didn't know his friend better, he would have sworn there was shame and regret in his tone. "the deer beer i brought ? it's not deer beer. not all of it. maybe 25%. or less. idk i lost track of how much heatisiac i added..."

Sans had a hard time understanding what Red was saying, but the name struck him as odd. Heatisiac ? As if reading his mixed up thoughts, Red provided an answer. "heatisiac is a prototype substance reducing a monster to a heatlike state. but without the pregnancy risks." Sans was sure now that even if he had been in his normal state, he wouldn't have understood what his friend was talking about. And he didn't even care. He needed Red to fuck him. Right. Now.

If he couldn't break free from Red's fists, he would address the other and more urgent matter : his burning crotch. He knew at this point any kind of friction would make him conjure ecto genitalia. And he was in desperate need of a pussy for Red to fuck. So he complied to his instinct and lifted his pelvis enough to rub against Red's groin.

"oooh...!"

That had felt sooo good... And for the both of them it seemed.

"fuuuck Sans i really need to tell you this but you make things so difficult for me. stop moving for a sec."

The only way Red found to do that was kissing Sans again. The blue skeleton took advantage of the incautious move and locked his arms against Red's neck, never to let him go. He also tilted his lower regions so that his newly formed ecto pussy would always be in contact with the tantalizing bulge in Red's pants. The gruff skeleton broke the kiss again, but this time Sans didn't complain as it was to lavish his neck with kisses and sweet bites. In between each nibble, he heard Red's voice, breathier than ever, and barely louder than a whisper : "Alphys was... testing the drug on... ff-fuck...me and -haaa- we wondered if we... would got... haaan the same reaction... on another me... oh fuck Sans you smell so good. i wanna fuck ya til you pass out i wanna make ya scream mah name _i wanna make you mine_!"

Without warning, Red tear Sans' pants off, revealing the trapped pussy, and didn't waste time in shoving two fingers in. It occured to Sans that it would have been painful if he wasn't already so wet. But now, it was almost not enough. He wasn't even aware his moans were so loud until Red silenced him with another kiss.

Then he felt what seemed to be the other's magic, right outside his entrance. With half opened eyelids he saw Red had conjured a deep crimson dick, with an impressive girth. He couldn't wait to be pounded into the couch by the ruby rod, but Red once again denied him the pleasure. He tilted his skull so that they were face to face.

"sweetie i need your consent before we do it. i only made you drink the beer to observe your reaction but it's gotten out of hand. i dont want you to feel forced to do this because of the drug. ive been crazy about you for half a year but ill understand if you dont wanna see me ever again after this. so while youre still sane enough to answer just tell me : do you want to do this _with me_ ?"

Suddenly something in Red's face changed. He appeared more colorful, the red on his cheeks was more vivid, and everything except his eyes blurred in Sans' vision. Without him realising it, Sans' eyelights had taken a heart shape.

"Red I love you."

**Author's Note:**

> end notes : “i only made you drink the beer to observe your reaction”, Red what the fuck ?! You redeem yourself with the consent thingy. BECAUSE CONSENT IS IMPORTANT GUYS. (but still wtf ?!)  
> I just kept thinking and couldn’t find a reasonnable explaination as to why the monsters in the Underground would know about Aphrodite, goddess of love, so in my head there was no way they would have come up with a name like “aphrodisiac”. That just made no sense to me. So heatisiac reduces a monster to a heat-like state, it lasts as long as a real one, but isn’t as dangerous if you choose not to do anything. It eventually wears off, while a real heat would just worsens if you don’t “treat” it. Also heatisiac doesn’t increases the odds of getting pregnant as a heat does. In the end it’s just a drug for horny monsters… Here, Red isn’t under the influence of the drug (because he put a lot of heatisiac in Sans’ drink but not in his own), he’s just affected by Sans’ “fake” heat.  
> Yes, Fell Alphys totally experimented on Red. Not that he complained : some G and free heatisiac for letting Alphys watch him go through multiple orgasms… Not a bad deal amaright ?


End file.
